The legislature shall establish, organize, and maintain a liberal system of public schools throughout the state for the benefit of the children thereof between the ages of seven and twenty-one years. The public school fund shall be apportioned to the several counties in proportion to the number of school children of school age therein, and shall be so apportioned to the schools in the districts or townships in the counties as to provide, as nearly as practicable, school terms of equal duration in such school districts or townships. Separate schools shall be provided for white and colored children, and no child of either race shall be permitted to attend a school of the other race.